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Enceladus: Hot at the Core?

by Paul Gilster | Mar 13, 2007 | Outer Solar System | 6 Comments

Every time we get new information about Enceladus, I keep thinking about how the original Orion team would have felt if they really had made the trip to Saturn they once discussed for their fabled atomic rocket. Enceladus, thought Freeman Dyson, looked to be a logical place to refuel because it was believed to be rich in ice and hydrocarbons. But no one in those pre-Cassini days could have imagined what Dennis Matson (Jet Propulsion Laboratory) is now talking about: "Deep inside Enceladus, our model indicates we've got an organic brew, a heat source and liquid water, all key ingredients for life. And while no one is claiming that we have found life by any means, we probably have evidence for a place that might be hospitable to life." All of which falls into the 'never in my wildest dreams' category, for Enceladus has hardly led the list when one discusses life's possible venues in the Solar System. But Cassini found geysers ejecting water vapor and ice from the moon's south polar...

Exobiology and the Press

by Paul Gilster | Mar 12, 2007 | Culture and Society | 16 Comments

When and if we discover extraterrestrial life, the handling of the news will be interesting. Recall the tumultuous media circus following the announcement in the movie Contact. Carl Sagan knew a little about dealing with the press, and the film version gets across what might happen when you start broadcasting public fear and fascination through a cable TV and Net-connected world. Or think of the recent rumblings when the SETI Institute said it was about to make a 'major announcement,' which turned out to be business related and not extraterrestrial at all. And in point of fact, we do have one actual experience of trying to announce extraterrestrial life. That was in 1996, when a team of researchers had submitted a paper, subsequently accepted, to Science. The contents were dynamite, for the authors proposed that the Antarctic meteorite ALH84001 might be evidence of life on Mars. The team had studied four potential biomarkers within the meteorite, which had earlier been determined to...

Whither the Science Fiction Magazines?

by Paul Gilster | Mar 10, 2007 | Culture and Society | 14 Comments

Back in the 1950's, science fiction magazines were all over the newsstands. That's significant for Centauri Dreams' purposes because these titles spurred many a career in science and a fascination with astronomy, astrophysics and engineering. Many is the scientist I've talked to who fondly reminisces about stories that proved inspirational, and in today's math-challenged world, getting students to start thinking about pursuing work in physics or other sciences is a serious concern. Which is one reason Paul Raven's recent essay on the declining fortunes of the science fiction magazines caught my eye. Paul writes Velcro City Tourist Board, the site I turn to when I want to know what's worth reading on the modern SF scene. He's well plugged in -- Paul writes reviews for Interzone, the fine British magazine, among other things -- and for those of us whose SF tastes run to older material, he provides a wonderful way of keeping up with new trends and making sense out of where the field is...

AEGIS: A Deep View of Galactic History

by Paul Gilster | Mar 9, 2007 | Deep Sky Astronomy & Telescopes | 0 Comments

Out near the end of the Big Dipper's handle is a strip of sky the width of two full moons that looks all but empty to the naked eye. But take a closer look, as the ongoing AEGIS survey is doing across the electromagnetic spectrum -- from radio and infrared through visible light up to the x-ray regions -- and you'll find more than 150,000 galaxies. AEGIS is examining galaxies up to 9 billion years back in time. The name stands for the All-wavelength Extended Groth Strip International Survey, and when I first wrote about it, I didn't have this link to the nineteen papers about the survey that will appear in the Astrophysical Journal Letters in the spring. What's exciting about the survey is its sheer breadth -- no other region of the sky this large has been examined quite so intensively. Cosmologist Jeffrey Newman (Lawrence Berkeley National Laboratory) puts it this way: "We have looked at this patch of sky with every possible telescope, at wavelengths covering nine orders of magnitude...

Sun Boosts Asteroid’s Spin

by Paul Gilster | Mar 8, 2007 | Asteroid and Comet Deflection | 8 Comments

OK, we sometimes encounter scientific terms with large numbers of syllables, but how about this one, perhaps the prize winner: the Yarkovsky-O'Keefe-Radzievskii-Paddack Effect. This multicultural monicker -- drawn on the names of a Russian engineer, an American scientist, a Russian astronomer and a NASA aerospace engineer -- has something interesting to say about sunlight. As solar radiation heats and cools an asteroid, released energy can change its rotation. In the case of the asteroid 2000 PH5, the effect increases the spin rate to the point where the asteroid may eventually come to spin faster than any asteroid known. This complicated study used a variety of telescopes to make the case that the asteroid's rotation period decreases by 1 millisecond every year. That's a long and slow effect, but the results build over time, and they're more readily observable because 2000 PH5 approaches Earth every year. The cause is the heating of the asteroid's surface by the Sun. Stephen Lowry...

Learning How Galaxies Form

by Paul Gilster | Mar 7, 2007 | Deep Sky Astronomy & Telescopes | 1 Comment

By analyzing a carefully selected set of 544 distant galaxies, researchers are beginning to learn how galaxies take their mature forms, becoming the glorious objects we see today. Sandra Faber (University of California at Santa Cruz), puts it this way: "We are now well on our way to seeing how galaxies evolved over the last half of the age of the universe. This work is not over, but the outlines of a theory are emerging." The galaxies in question weigh in with redshifts in the range of 0.1 to 1.2, which translates to 'look-back' times of between 2 and almost eight billion years. These adolescent galaxies are far more disordered than nearby ones, but it turns out that the relationship between a galaxy's mass and the orbital speed of its stars and gas is consistent over different types of galaxy and over billions of years of galactic evolution. In other words, the more massive a galaxy is, the faster the stars and gas inside it move. That analysis includes a 'dispersion component' that...

Asteroids: The Threat and the Budget

by Paul Gilster | Mar 6, 2007 | Asteroid and Comet Deflection | 5 Comments

NASA is putting the number of potentially hazardous asteroids and comets at 20,000 in a report that will be released later this week, according to an AP story now circulating. And the report, reviewed at a Planetary Defense Conference in Washington yesterday, pegs the cost of finding 90 percent of these objects at $1 billion. That's bad news for those worried about Earth-crossers. For AP quotes NASA Ames director Simon Worden: "We know what to do; we just don't have the money." And as Larry Klaes wrote me this morning, "But just imagine the bill after a big space rock hits Earth." NASA is already tracking some 769 objects in a search now described as behind schedule. From the story: One solution would be to build a new ground telescope solely for the asteroid hunt, and piggyback that use with other agencies' telescopes for a total of $800 million. Another would be to launch a space infrared telescope that could do the job faster for $1.1 billion. But NASA program scientist Lindley...

Philosophia Naturalis #7 Now Available

by Paul Gilster | Mar 6, 2007 | Culture and Society | 0 Comments

The seventh iteration of Philosophia Naturalis is now online at geek counterpoint. These 'blog carnivals' are increasingly helpful because they cluster articles of interest, and I always wind up learning about new things to read. This carnival's find is Rob Knop (Vanderbilt), whose Galactic Interactions blog offers an intriguing entry on what he calls 'The Greatest Mystery in All of Physics," which turns out to be the link between gravitational and inertial mass. Another find: Cosmic Variance's take on relativity and why E=mc2. Which gets us into a thought experiment: Think of a physicist, standing at one side of a large box, which itself is sitting on a perfectly frictionless surface (think of ice if you like). The physicist possesses a large cannon, which she is using to hurl heavy cannonballs across the box. What happens to the whole system? The answer is informative and entertaining, particularly when you replace the cannon with a powerful laser. Read the rest at the site, and...

Solar Sail Mission to an Asteroid

by Paul Gilster | Mar 5, 2007 | Sail Concepts | 0 Comments

If you're looking to shake out a solar sail design, a near-Earth asteroid (NEA) makes a tempting target. It's relatively close and offers the opportunity of a landing and sample return. That helps us work out the age, evolution and other characteristics of a class of objects that are potentially dangerous to our planet. It's no surprise, then, that when DLR, the German Aerospace Center, went into serious solar sail studies, it began to develop a dedicated mission via sail to one or more NEAs. That was in August of 2000, and it built on DLR's successful ground deployment of a square solar sail 20 meters to the side the previous December, conducted in a simulated weightless environment (see below). The DLR design is a square sail with four triangular sail segments, a valuable proof of concept in a time when little budgetary emphasis is being placed on sail designs by any of the major space agencies. Image: DLR's deployed solar sail, seen at the Center's facility in Cologne. Credit:...

Deep Water and Europa

by Paul Gilster | Mar 3, 2007 | Autonomy and Robotics | 16 Comments

If humans ever do establish a presence on Europa, it will surely be somewhere under the ice. Assuming, that is, that the ice isn't too thick, and to learn about that we have to await further study, and probably a Galilean moon orbiter of some kind that can observe Europa up close and for lengthy periods. But assuming the ice is more than a few meters thick, it should provide radiation screening, and getting down into that presumed Europan ocean is where we want to be in the search for life. Of course, the first undersea explorations on the Jovian moon will have to be robotic, and here we can talk about technologies under development today. NASA has funded a self-contained robot submarine called the Deep Phreatic Thermal Explorer (DEPTHX) that operates with an unusual degree of autonomy, navigating with an array of 56 sonar sensors and an inertial guidance system. Now a series of tests in Mexico at a geothermal sinkhole, or cenote, called La Pilita have tested out key components,...

A Call for Exoplanet Studies

by Paul Gilster | Mar 2, 2007 | Exoplanetary Science | 0 Comments

Passed along by Greg Laughlin (UC-Santa Cruz), this call for papers: The ExoPlanet Task Force (ExoPTF), an Astronomy and Astrophysics Advisory Committee (AAAC) subcommittee formed at the request of NSF and NASA, announces a call for white papers to inform their assessment of techniques and approaches for extra-solar planet detection and characterization, using both space- and ground-based facilities. The ExoPTF has been asked to recommend a 15-year strategy to detect and characterize exoplanets and planetary systems, and their formation and evolution, including specifically the identification of nearby candidate Earth-like planets and study of their habitability. White papers may describe studies, measurements with existing facilities, new instruments, new facilities or missions, considerations from theoretical modeling, or other recommendations or information that can support the Task Force in its work as laid out in the charge. Submission instructions and other information can be...

Reflectivity and Its Opposite

by Paul Gilster | Mar 2, 2007 | Exotic Physics | 1 Comment

We've just been discussing extraordinarily reflective mirrors for advanced propulsion. Here's the inverse, in a story from ScienceNOW: Scientists have created the world's first film that casts practically no reflection. A vast improvement over current nonreflective materials, the new technology could revolutionize solar cells, intensify light-emitting diodes, and possibly help solve mysteries in quantum mechanics by mimicking a "black body," an object that absorbs all light. The new coating reflects no light across much of the visual spectrum. This work, done at Rensselaer Polytechnic Institute, seems to have enormous potential for increasing solar cell efficiency. Much more here.

Close Pass by Jupiter

by Paul Gilster | Mar 2, 2007 | Outer Solar System | 5 Comments

New Horizons' close approach to Jupiter on the 28th of February set up some intriguing observational possibilities. The Pluto-bound spacecraft now moves beyond the giant planet in a trajectory that takes it down Jupiter's 'magnetic tail,' where sulfur and oxygen particles from its magnetosphere eventually dissipate. Since no spacecraft has ever been in this region before, coordinating what New Horizons sees with other instruments -- both space-based and terrestrial -- can tell us much about the Jovian environment. The image below is a composite of data from the Chandra X-ray Observatory superimposed upon the latest Hubble image. Notice the x-ray activity near the poles, where Chandra is detecting aurorae. The operative mechanism seems to be interaction between the solar wind and the sulfur and oxygen ions in Jupiter's magnetic field, creating aurorae a thousand times more energetic than what we see on Earth. Image: In preparation for New Horizon's approach of Jupiter, Chandra took...

Laser Bounce to the Stars

by Paul Gilster | Mar 1, 2007 | Sail Concepts | 17 Comments

Via advanced nanotechnology, the news that the Solid State Heat Capacity Laser (SSHCL) has achieved 67 kilowatts of average output power in the laboratory. Six to eight months of additional work are needed, it is believed, to reach the 100 kW mark. Which sets Brian Wang to pondering a "...proof of concept photonic laser propulsion system using mirrors to bounce laser light and multiply the effectiveness of lasers generate 35 micronewtons of thrust using low wattage lasers and 3000 bounces." Wang then quotes from a paper on multi-bounce methods by Geoffrey Landis and Robert A. Metzger. A major problem in laser lightsail techniques is reducing the power requirement, which can be onerous: It has been proposed that extremely small payloads (10 kg) could be delivered to Mars in only 10 days of travel time using laser-based lightsail craft (Meyer, 1984), but in order to do so, would require a 47 GW laser system. And if we start thinking interstellar, the laser numbers go sharply up. We're...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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